Spiral conveyor system

ABSTRACT

A spiral conveyor system may include a drum associated with a motor, wherein the drum extends from a drum bottom to a drum top. In addition, the system may include a conveyor belt traveling helically about the drum from an entrance end of the drum to an exit end of the drum. Further, the system may include a rib associated with the drum, wherein the rib extends radially from a surface of the drum, and at least one drive face positioned on the rib. The conveyor belt may include at least one belt surface configured to engage the at least one drive face. The length of the rib extends along the length of the drum from a first end of the rib to a terminus of the rib proximate the entrance end of the drum. In addition, the drum includes a ring that extends between the terminus of the rib and the entrance end of the drum.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of Neely et al., U.S. Patent Appl.Publ. No. 2018/0290833, published Oct. 11, 2018, and entitled “SpiralConveyor System,” which is a continuation of Neely et al., U.S. PatentAppl. Publ. No. 2017/0022012, published Jan. 26, 2017, and entitled“Spiral Conveyor System,” which claims priority under 35 U.S.C. § 119(e)to U.S. Provisional Patent Application No. 62/196,582, entitled “SpiralConveyor System,” and filed on Jul. 24, 2015, which applications arehereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to positive drive systems for spiralconveyor belts. In particular, the invention relates to a drum withribs, where the drive face for engaging the conveyor belt is on the riband where the rib height above the surface of the drum varies.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments can be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale though the scale shown may be considered oneembodiment, emphasis instead being placed upon illustrating theprinciples of the embodiments. Moreover, in the figures, like referencenumerals designate corresponding parts throughout the different views.

FIG. 1 shows a schematic diagram of a spiral conveyor system;

FIG. 2 is an enlarged partial perspective view of a portion of a spiralconveyor system showing engagement of a conveyor belt with driveelements of the system;

FIG. 3 is an enlarged partial plan view of a portion of a spiralconveyor system showing engagement of a conveyor belt with driveelements;

FIG. 3A is an enlarged plan view of a portion of a spiral conveyorsystem showing a portion of a drum and the engagement of different tiersof a conveyor belt with the drum;

FIG. 4 is an enlarged perspective view of a top portion of a spiralconveyor system showing engagement of a conveyor belt with driveelements of the system;

FIG. 4A is a cross-sectional view of a drive element of the system ofFIG. 4, taken along line 4A-4A;

FIG. 5 is an enlarged plan view of a portion of a spiral conveyor systemshowing engagement of a conveyor belt with drive elements that includecaps;

FIG. 6 is a partial perspective view of a portion of a spiral conveyorsystem showing two belt tiers and engagement of the conveyor belt withdrive elements;

FIG. 7 is a partial perspective view of a portion of a spiral conveyorsystem showing two belt tiers and engagement of the conveyor belt withdrive elements;

FIG. 8 is an enlarged perspective view of a spiral conveyor systemshowing drive elements with cage bar caps each having a protruding ribhaving a drive face to engage with the conveyor belt;

FIG. 9 is a perspective view of a cage bar cap having a protruding rib;

FIG. 9A is a cross-sectional view of the cage bar cap of FIG. 9, takenalong line 9A-9A;

FIG. 10 is a perspective view of another embodiment of a cage bar caphaving a protruding rib;

FIG. 10A is a cross-sectional view of the cage bar cap of FIG. 10, takenalong line 10A-10A;

FIG. 11 is an enlarged perspective view of a spiral conveyor systemshowing drive elements with integrated protruding ribs;

FIG. 12 is a perspective view of a cage bar cap having an offset andchamfered protruding rib;

FIG. 12A is a cross-sectional view of the cage bar cap of FIG. 12, takenalong like 12A-12A;

FIG. 13 is a partial enlarged plan view of a conveyor belt engaged witha rib of a cage bar cap;

FIG. 14 is a partial enlarged plan view of a conveyor belt engaged withan elongated rib of a cage bar cap;

FIG. 15 is a partial enlarged plan view of a conveyor belt engaged withan elongated rib of a cage bar cap and a support surface;

FIG. 16 is an enlarged perspective view of the system shown in FIG. 15,a conveyor belt engaged with an elongated rib of a cage bar cap and asupport surface;

FIG. 17 is a partial plan view of a portion of an embodiment of a spiralconveyor system with drive elements with cage bars and cage bar caps,wherein the cage bar caps include protruding ribs;

FIG. 18 is an enlarged view of another embodiment of a drive elementengaged with a conveyor belt;

FIG. 19 is an enlarged view of an embodiment of a drive element engagedwith a conveyor belt showing the clearance between the rib and the belt;

FIG. 20 is an enlarged view of an embodiment of a drive element engagedwith a conveyor belt showing the clearance between the rib and abuttonhead of the belt;

FIG. 21 is an enlarged plan view of an embodiment of a drive system fora conveyor belt showing an engaged drive element and a disengaged driveelement;

FIG. 22 is an enlarged perspective view of a bottom of a spiral conveyorsystem showing drive elements with cage bar caps each having aprotruding rib having a drive face to engage with the conveyor belt anda smooth belt entrance surface;

FIG. 23 is a perspective view of an embodiment of a bottom of a spiralconveyor showing the belt engaging with the drive elements having asmooth belt entrance surface;

FIG. 24 is an enlarged perspective view of an embodiment of anengagement of an edge link of a conveyor belt with a drive element thathas a protruding rib and a support surface;

FIG. 25 is a perspective view of an embodiment of a bottom of a spiralconveyor showing the belt engaging with a ring having a smooth beltentrance surface; and

FIG. 26 is a perspective view of an embodiment of a top of a spiralconveyor showing a belt disengaging from a drum.

DETAILED DESCRIPTION

For clarity, the detailed descriptions herein describe certain exemplaryembodiments, but the disclosure in this application may be applied toany positive drive spiral conveyor system including any suitablecombination of features described herein and recited in the claims. Inparticular, although the following detailed description describescertain exemplary embodiments, it should be understood that otherembodiments may be used for positive drive spiral conveyor belts withcontoured drive elements.

The spiral conveyor system discussed below is generally a positive drivesystem, where a drive element comes into direct contact with theconveyor belt to propel the conveyor belt in a travel direction. In thesystems discussed below, a central rotating drum includes drive elementsthat include a drive face for engaging with the conveyor belt. The driveface on the drive element may be adjacent a contoured surface of thedrive element, such as a rib that protrudes from the drum or a surfaceof the drive element. The rib may provide improved geometry for thedrive face and also may smooth the travel of the conveyor belt up ordown the spiral, particularly when the rib itself has varying heightabove the drum surface. The conveyor belt may also include a provisionto enhance the engagement with the rib, such as a protrusion or a tabwith a flat surface for better contact with the drive face.

FIG. 1 shows an embodiment of a spiral conveyor system 1 that mayutilize at least one contoured drive element drive system. Spiralconveyor systems such as spiral conveyor system 1 are well known in theart. Spiral conveyor system 1 may include a conveyor belt 15 that isconfigured to travel a spiral column 5 around a driving drum 10. In someembodiments, driving drum 10 may include one or more drive elements 20that engage with conveyor belt 15 for a positive drive system, where thefrictional and/or geometric engagement of the drive elements 20 withconveyor belt 15 impart forward motion to conveyor belt 15. In someembodiments, driving drum 10 and the edge of conveyor belt 15 mayinclude provisions that engage with each other to transfer driving forcefrom the turning drum to the conveyor belt.

Drum 10 may be configured to rotate at various RPM (revolutions perminute), but may be configured to turn at low RPM. The precise speed maydepend upon factors such as the height of spiral column 5, the length ofbelt 15, and the intended use of the system, such as to establish aparticular cooking, baking, or freezing time. In some embodiments, drum10 may turn at 15 RPM or less. In some embodiments, drum 10 may turn at10 RPM or less. In some embodiments, drum 10 may turn at 4 RPM or less.In some embodiments, drum 10 may turn at a rate between 0.1 RPM and 10RPM, inclusive.

Drum 10 may be rotated using any method known in the art, such as with amotor (not shown) positioned proximate a base 103 of spiral conveyorsystem 1. The motor may transfer the power it generates to drum 10 usingany mechanism known in the art. In some embodiments, such as theembodiment shown in FIG. 1, known systems, such as chains and gear boxesto control the transfer of power from the motor to shaft 106, may beprovided. Shaft 106 may be any type of drive shaft known in art, such asan elongated metal pole that extends from base 103 to the top of spiralcolumn 5 along drum central axis 3. One or more struts such as strut 109may attach shaft 106 to drum 10 to transfer the rotational force ofshaft 106 to drum 10. Drum 10 may be generally cylindrical in shape andmay, in some embodiments, include a cylindrical surface 11 as shown inFIG. 6. The cylindrical surface may be a continuous cylindrical drumsurface formed of sheet metal, or may have a discontinuous surfaceformed of individual vertical drive elements extending between andconnecting circular support bands arranged about the center axis of thedrum, or may be a combination of sheet metal and vertical bars as shownin FIG. 1. Other construction is contemplated to provide a suitablecylindrical surface for guiding an inside edge of belt 15 through spiralcolumn 5. Drive elements 20 may comprise a contoured rib attached to thesheet metal surface of the drum, such as in the embodiments shown inFIGS. 2-7, or to a cage bar, as shown in FIGS. 8-26 where the ribextends from a surface of a cage bar cap, or may comprise a combinationof a cage bar and a contoured rib. Drive elements 20 may also comprise acap or covering, such as to provide the contoured surface and/or forimproved wear properties, such as shown in FIGS. 4 and 4A.

A bottom bearing 101 may be provided in, on, or associated with a motor,gearbox, and/or a conveyor frame. As is known in the art, a bottombearing 101 is provided to reduce rotational friction between the motorand/or base 103 and shaft 106 while supporting radial and axial loads.Bearings and their functionality are generally well known and understoodin the art.

Conveyor belt 15 may be modular and include links 25 and connecting rods26 as shown in FIG. 2. Conveyor belt 15 may be any type of endless beltknown in the art. Conveyor belt 15 may be made from metal, plastic,composites, ceramics, combinations of these materials, or any other typeof conveyor belt material known in the art. The particular material maybe selected based on factors such as temperature exposure (baking,freezing, room temperature conveying), required tension, length of thebelt, ability to clean and/or disinfect the belt, etc. In someembodiments, such as the embodiment shown in FIG. 1, belt 15 may be anupgoing belt, where belt 15 travels from a bottom 64 of spiral column 5to a top 63 of spiral column 5. In other embodiments, the direction oftravel may be downgoing, where belt 15 travels from top 63 to bottom 64.Belt paths at top 63 and bottom 64 may be aligned as shown or arrangedat an angle with respect to each other about a central axis 3 of drum10.

In use, a conveyor belt 15 enters at one end of drum 10, typicallybottom 64. Conveyor belt 15 may be fed into the system 1 off of tworollers or sprockets positioned on an axle. Conveyor belt 15 travelsthrough stacked helical tiers around the center drum 10. Conveyor belt15 then exits at the opposite end of drum 10, typically near top 63.Conveyor belt 15 may be an endless belt 15, in which case conveyor belt15 is fed back to the axle/sprocket at the other end of drum 10 (e.g.,in one embodiment, belt 15 travels back to bottom 64 of drum 10 afterexiting at top 63 of drum 10.) In any embodiment, however, the systemmay be upgoing (traveling from bottom to top) or downgoing (travelingfrom top to bottom). The gearing and optional weighting of belt 15 atthe entrance and/or exit points of spiral 5 may be configured to assistin controlling tension in belt 15 as belt 15 moves through the system 1.For example, system 1 may include a take-up sprocket 115 configured topull belt 15 out of spiral column 5. Take-up sprocket 115 may be locatedat or after the first terminal roller. Take-up sprocket 115 may beindependently driven, such as with a motor 116. In some embodiments, themotor may be a constant torque motor so that the tension in belt 15 maybe controlled within a desired range. In some embodiments, a weightedtake-up roller 117 may be provided to assist in maintaining the belttension along return path 104 and to remove slack belt from the system.Proper tension in belt 15 may inhibit operational issues such asslippage of belt 15 with respect to drum 10, belt flip-up, or difficultyfeeding belt 15 into or out of the helical stack.

In some embodiments, the first tier 80 of belt 15 at the entrance end(e.g., bottom 64) has a first larger radius and the last tier of belt 15at the exit end has a second smaller radius. For example, FIG. 3A showstwo different tiers, first tier 80 and second tier 90, of belt 15 madeof links 125 and elongated rods 126 that connect the links together.Drum 10 may have a first radius R1 supporting first tier 80 and a secondsmaller radius R2 supporting second tier 90. First radius R1 may be at alower position on drum 10 than second radius R2. Belt 15 may be held ateither radius by engagement of the circumferential support surfaces ofbelt 15 with circumferential support surfaces of the drive elements 20,which are discussed in more detail below with respect to otherembodiments.

In some embodiments, belt 15 may have circumferential support surfacesand driving surfaces on the inner edge of belt 15 configured to engagethe drive elements. An example of such a belt configuration is shown inFIG. 3 which shows a partial plan view of the embodiment of the spiralsystem shown in FIG. 2. In FIG. 3, the engagement between the edge link27 and drive element is clearly shown. Belt 15 may include a protrusion14 configured to engage the driving face 45 of driving element 20 atengagement point 22. In some embodiments, protrusion 14 may be a tab orflange extending from an outside surface of edge link 27. In someembodiments, protrusion 14 may be a portion of a connecting rod 26. Inthe embodiment of FIG. 2, driving element 20 comprises a contoured ribthat extends between lower support ring 75 and upper support ring 85 andis configured to fit between adjacent belt protrusions 14. Drive element20 has a contoured circumferential support surface 23 and a driving face45 shown in FIG. 3. Due to the direction of travel, the relativeposition of protrusion 14 and drive element 20 is such that driveelement 20 is trapped behind protrusion 14. Therefore, driving element20 can push against protrusion 14. Belt 15 may also includecircumferential support surfaces on edge links 27 configured to engage acircumferential support surface of a driving element to hold the belt ata predetermined radius.

FIGS. 4 and 4A show a portion of a top of drum 10, where each driveelement 20 includes a contoured rib 31 and a rib cover or wear cap 41.In the embodiment shown in FIG. 4, wear cap 41 follows the contouredsurface of contoured rib 31 and provides drive face 45 shown in FIG. 3for engaging conveyor belt 15. In the embodiment shown in FIG. 4, cagebar caps 40 are separate and distinct from contoured ribs 31 and areattached to contoured ribs 31. In some embodiments, the attachment maybe fixed and permanent, such as by welding, using adhesives, or withrivets. In other embodiments, the attachment may be removable, such aswhen press-fitted, interference-fitted, with screws, clips, or the like.

FIG. 4A, a cross-section of a driving element from FIG. 4, shows thatcontoured rib 31 is distinct from wear cap 41. As shown in FIG. 4A,contoured rib 31 is solid in cross-section and wear cap 41 is athree-sided, U-shaped portion of material that is sized and shaped tofit over and partially surround contoured rib 31 so that wear cap 41faces outward towards belt 15. In other embodiments, contoured rib 31may be hollow or have any other cross-sectional shape. As shown in FIG.4, wear cap 41 is oriented on contoured rib 31 so that wear cap 41 facesconveyor belt 15. In this embodiment, wear cap 41 may be attached tocontoured rib 31 using any of the methods discussed above. In thisembodiment, wear cap 41 may act as a lower coefficient of friction coverof contoured rib 31 and simply follow the contours of contoured rib 31.Although shown as generally parallel to the belt edge, contoured surface23 may be angled or have a chamfered edge, and wear cap 41 may becorrespondingly angled with a chamfered edge to improve engagement withthe belt.

Contoured rib 31 may be made of any material, such as metal, plastic, orcomposite. Wear cap 41 may be made of the same material as contoured rib31 or a different material. For example, in a typical embodiment,contoured rib 31 may be made from a metal while wear cap 41 may be madefrom a plastic material. In other embodiments, contoured rib 31 may bemade from a plastic material and wear cap 41 may be made from the sameplastic material. In other embodiments, contoured rib 31 may be madefrom a plastic material while wear cap 41 may be made from a differentplastic material. Any combination of materials may be appropriatedepending upon the intended use. For example, both contoured rib 31 andwear cap 41 may be made from the same metal or metals having similarthermal expansion properties for baking embodiments. Similarly, bothcontoured rib 31 and wear cap 41 may be made from the same plasticmaterial or plastic materials having similar low temperature propertiesfor freezing embodiments. Further, wear cap 41 may be made from amaterial with a lower coefficient of friction and/or more durable wearproperties than contoured rib 31 for long-term engagement with conveyorbelt 15. In some embodiments, wear cap 41 may be a sacrificial wearcomponent.

FIG. 5 shows a partial plan view of the embodiment of the spiral systemshown in FIG. 4. In FIG. 5, the engagement between the edge link 27 andwear cap 41 is more clearly shown. Wear cap 41 follows a contouredsurface of contoured rib 31, creating a circumferential support surface46 on wear cap 41 for contacting corresponding outer edge surface 28 ofedge link 27 belt 15. Wear cap 41 also covers a driving face ofcontoured rib 31, creating a driving face 45 on wear cap 41 for engagingprotrusion 14 of belt 15. Due to the direction of travel, the relativeposition of protrusion 14 and wear cap 41 is such that wear cap 41 istrapped behind protrusion 14. Wear cap 41, and, therefore, drivingelement 20 can push against protrusion 14.

Contoured surface 23 shown in FIG. 4 may have any combination of curved,tapered, and flat portions. In some embodiments, contoured surface 23varies the height of the drive face above drum surface 11. This heightvariation allows for improved tension control as belt 15 travels alongspiral tower 5. In some embodiments, contoured surface 23 is arranged sothat as belt 15 follows the contour, the height either remains constantor decreases—the height does not increase in the direction of beltmovement. This constant or decreasing height of contoured surface 23above drum surface 11 serves to prevent increases in belt tension thatwould otherwise result from increasing the radius of a tier of belting.

FIG. 6 shows two tiers of an edge driven system with contoured driveelements showing the relative position of the two tiers at differentheights on spiral tower 5. In this embodiment, drive element 20 is acontoured rib attached to drum 10, where drive element 20 includes acontoured surface 23 that has three sections of varying height abovedrum surface 11: a lowest section 91 that extends the furthest away fromdrum surface 11, an upper section 92 whose surface is closer to drumsurface 11 than a surface of lowest section 91, and a tapered section 93that connects lower section 91 and upper section 92. In this embodiment,lower section 91 and upper section 92 are both flat, with unvaryingheight above drum surface 11 within the discrete section. In otherembodiments, any section may include subsections with varying heightand/or continuous tapers like tapered section 93.

Contoured surface 23 positions belt 15 at different radii depending uponthe position of belt 15 on drum 10. First tier 80 is positionedproximate a bottom 64 of drum 10 on lower section 91 of driving element20. Second tier 90 is positioned proximate top 63 of drum 10 on uppersection 92 of driving element 20. Lower section 91 is the highest partof contoured surface 23 while upper section 92 is closer to drum surface11 than lower section 91. Therefore, first tier 80 is positioned furtheraway from drum surface 11 than second tier 90. The loop of first tier 80around drum 10 has a greater radius than that of second tier 90. As aweighted roller often assists in the take-up of belt 15 when exitingspiral 5 as shown by weighted roller 117 in FIG. 1, the smaller radiusproximate the spiral exit may help to produce a constant tension in belt15 in all tiers of spiral 5. FIG. 7 shows a similar arrangement of firsttier 80 and second tier 90 but on drive elements 20 that have a constanttaper in the lower portion that is furthest away from drum surface 11 atbottom 64 and a constant height in the upper portion closest to drumsurface 11 at exit point 67.

The embodiments shown above with respect to FIGS. 2-7 show embodimentsthat may be particularly suitable for high temperature uses, such ascooking and baking. Oven and/or cooker drums are generally constructedas cages, such as is best shown in FIG. 4, or as continuous sheet metalcylinders, such as is best shown in FIGS. 6 and 7. While rapid wear dueto contact between the drum and belt is typically tolerated, someexpensive high temperature plastics such as PEEK (poly ether etherketone) may be used to increase the life of the parts. However, the highcosts and more rigid mechanical properties may make PEEK and similarmaterials undesirable. Therefore, while any material may be appropriatefor the drive components, all drive components in the embodiments shownin FIGS. 2-7 may be made from metals to be cost effective and relativelyeasy to machine/manufacture. However, in an embodiment such as theembodiment shown in FIG. 4, a relatively small wear cap 41 is provided.Wear cap 41 has a much smaller cross-sectional area than a standard cagebar cap, such as the cage bar cap 140 shown in FIGS. 9 and 9A below. Assuch, a small wear cap like wear cap 41 may be cost-effective to producein PEEK or a similar high temperature material.

In contrast, the embodiments shown below with respect to FIGS. 8-26 maybe manufactured for lower temperature systems, such as for any use atless than about 100 degrees C., for example room temperature conveyingor freezing operations. In such embodiments, a wider variety ofmaterials may be used for the drive surfaces. In many embodiments, adrum may be constructed in a typical cage configuration, with upper andlower rings connected by vertical cage bars, such as shown in FIG. 8. Incage bar embodiments, the cage bars may be covered with cage bar capsmade from inexpensive materials for use as sacrificial wear components.A typical material is UHMW (ultra high molecular weight polyethylene).Such inexpensive wear materials may not be appropriate for highertemperature applications due to glass transition and melt temperatures.However, for lower temperature systems, UHMW and similar materials areeasily extruded, even when including a protruding and, in someembodiments, contoured rib. Machining such a rib is also readilyachieved. These lower cost manufacturing abilities make suchfabrications even lower cost than forming similar structures from metalssuch as steel. Further, because UHMW and similar materials may besomewhat soft, cage bar caps made from UHMW may be readily manipulatedto snap onto a cage bar. Finally, such UHMW cage bar caps may be used toretrofit existing systems with ribbed cage bar caps by simply replacingan existing ribless cage bar cap with a ribbed cage bar cap,particularly when installing the ribbed cage bar in a freezer or otherhard-to-access system where the cage bar may be bent to be maneuveredinto the proper position.

In some embodiments, contoured surface 23 may also include additionalgeometry to better engage belt 15. FIGS. 8-26 show various embodimentsof drive elements 20 that include a rib that protrudes from the surfaceof drive elements 20 toward belt 15. These ribs include the heightvarying contoured surface 23 and also provide a drive face configured tocontact a portion of belt 15, such as a tab on an edge link as discussedabove.

FIG. 8 shows a partial perspective view of a drum 8010 that includesdrive elements 8020. Rib 8021 is a protrusion that extends away from abase surface 8032 of cage bar cap 8040 towards belt 8015 and establishesa contoured surface 8023. Similar to contoured surface 23 discussedabove with respect to FIG. 6, contour surface 8023 includes a flat lowersection 8041 at a first height above base surface 8032, an upper section8043 at a second, lower height above base surface 8032, and a taperedsection 8047 that continuously joins lower section 8041 to upper section8043. A leading edge 8046 of rib 8021 may include a drive face 8045 thatengages with belt 8015. In some embodiments, belt 8015 may engage thedrive face 8045 with the end surface 8028 of a link leg 8018.

FIGS. 9 and 9A show another embodiment of a cage bar cap 140 with anoffset rib 121 that may be used in a spiral system such as the systemshown in FIG. 8. In this embodiment, cage bar cap 140 is a structureconfigured to fit onto cage bar 8030 and includes a body with four wallsthat define an interior cavity 143: a first wall 130, a second or frontwall 132, third wall 133, and an open, discontinuous fourth wall thatincludes a fourth wall first portion 134 and a fourth wall secondportion 135. Cavity 143 is configured to receive a cage bar (not shown),so that first wall 130, second wall 132, third wall 133, and fourth wallportions 134, 135 cover the cage bar. While first wall 130, second wall132, third wall 133 may fully cover a corresponding cage bar wall,discontinuous fourth wall portions 134, 135 will only cover a portion ofa corresponding cage bar wall, as a gap 136 between fourth wall firstportion 134 and fourth wall second portion 135 allows a cage bar to beinserted into cavity 143 or allows for some give in cage bar cap 140 topermit cage bar cap 140 to slide onto a cage bar. Cage bar cap 140 maybe made of any metal or synthetic material.

Cage bar cap 140 may be oriented on a cage bar so that front wall 132 isconfigured to face a conveyor belt (not shown) when cage bar cap 140 isinstalled in a spiral system.

Cage bar cap 140 includes a rib that extends away from the body. In thisembodiment, offset rib 121 protrudes away from a base surface 142 offront wall 132 to a rib height, and a length of offset rib 121 iscoextensive with a top-to-bottom length of cage bar cap 140. In thisembodiment, rib height varies along the length of offset rib 121.Similar to embodiments discussed above, offset rib 121 includes threecontinuous portions: an upper section 110, a lower section 111, and atapered section that connects upper section 110 and lower section 111.Upper section 110 extends a first height 151 above cage bar cap surface142, where first height 151 is constant; tapered section 112 extends asecond height 152 above cage bar cap surface 142, where second heightvaries along the length of tapered section 112; and lower section 111extends a third height 150 above cage bar cap surface 142. In thisembodiment for an upgoing belt, third height 150 is greater than firstheight 151, while second height 152 tapers from third height 150 tofirst height 151. In other embodiments where the belt is downgoing,offset rib 121 may be inverted.

Third height 150 may be based on several factors, including the size ofthe drum, the tension of the incoming belt, and the elasticity of thebelt. Third height 150 may be chosen to create an increase in thecircumference of a first tier of belting approximately equal to or asignificant percentage of the amount of stretch in the belt. In thisway, when the belt moves to a position around the second lower ribheight, there will be very little stretch, and hence tension, remainingin the belt.

First height 151 may be determined by the height of any edge featuresfor engaging with the drive cap, such as protrusions 14 shown in FIG. 5.In some embodiments, offset rib 121 may be designed so that an end of anedge feature is configured to contact the face 142 of the cage bar cap140. In other embodiments, offset rib 121 may be designed so that an endof an edge feature does not contact face 142 of cage bar cap 140. Thischoice is typically based on wear considerations. For example, the endof an edge feature on a metal link may be rough or sharp as a result ofthe link being punched from sheet metal material. In this case, it maybe advantageous for offset rib 121 to support the link away from face142 and prevent the rough end surface of an edge feature from wearingface 142 of cage bar cap 140. In the case of a molded plastic link, itmay be preferable to design a flat wear surface on the end of theprotrusion specifically to contact face 142 of the cage bar cap 140 toposition a link or prevent wear on a tension-bearing portion of thelink.

Taper angle 125 may be restricted by factors such as the belt tension,belt weight, and friction coefficient between the belt and cage bar cap.Taper angle 125 may be limited so that the radial force created by thebelt tension is inhibited from causing an inside edge of the belt tolift off the support rails and move upward along the taper toward aportion of the drum with a smaller radius. In this regard, higher beltweight and higher coefficient of friction will also inhibit suchmovement. A minimum length of the taper may be determined by thedifference in height between the first height 151 and second height 150and the maximum taper angle 125 that will inhibit lifting the insideedge of the belt. However, the length of tapered section 112 can be aslong as desired and may be as long at the offset rib 121 itself, e.g.,offset rib 121 may have a continuous taper along a length of offset rib121 so that offset rib 121 may have a continuously variable height.

In some embodiments, third height 150 may be between one-half (½) inchto two (2) inches. First height may be between ¼ inch to ⅜ inches.Tapered section 112 may taper at an angle 125 that is 30 degrees or lessfrom third height 150 to first height 151. In other embodiments, any ofthese heights may be greater or lower than these ranges.

Offset rib 121 has a thickness 147. In this embodiment, thickness 147 isconstant along the entirety of offset rib 121. Thickness 147 may beselected based on a number of factors, but is generally proportional tothe rib height; when height of offset rib 121 increases, so doesthickness 147. In such embodiments, the height-thickness proportion maybe selected based upon the highest rib height, such as third height 150in the embodiment shown FIG. 9. In some embodiments, offset rib 121 isstructurally rigid enough to drive the belt without significantdeflection, which may be considered to be more than approx. 5° from basesurface 142, i.e. remaining at an angle that is 90° to 95° with respectto the face of cage bar cap). However in some embodiments, a positivedrive system can operate with a drive face that is not perpendicular andis angled as much as 45° with respect to the face of the cage bar cap(i.e., ranging from 45 degrees to 135 degrees with respect to the cagebar cap), depending on belt tension, friction, etc. In such embodiments,any drive face may be correspondingly angled (as is known in the art,sprocket and gear faces are generally angled or curved in this way). Inthose embodiments where a conveyor belt includes edge features forengaging with the drive cap, such as protrusions 14 shown in FIG. 5,thickness 147 may be limited by any spacing between those belt edgefeatures so that thickness 147 does not exceed that interstitialspacing. This spacing may vary as the belt may be collapsible toaccommodate the curves of the spiral. In such cases, thickness 147 maybe selected to accommodate the minimum spacing—the spacing between edgefeatures when the belt is fully collapsed. Similar thicknessrestrictions may be placed on any rib discussed herein, including driveelement 20 discussed above with respect to FIGS. 2-7.

In the embodiment shown in FIGS. 9 and 9A, offset rib 121 is positionedproximate third wall 133. As such, offset rib 121 is shifted away from acentral axis 100 of cage bar cap 140 an offset D2 and is positioned afirst distance D1 away from leading face 130. This offset may bebeneficial in stiffening offset rib 121 due to additional support fromthird wall 133. Additionally, because offset rib 121 is essentially asmooth extension of third wall 133, a crevice is eliminated, which mayinhibit an accumulation of debris on cage bar cap 140 and/or may makecage bar cap 140 easier to clean. It may also be easier to machine thecontour of offset rib 121 by laying third wall 133 flat on a machiningsurface.

FIGS. 10 and 10A show a cage bar cap 240 that is essentially the same ascage bar cap 140, except that central rib 221 is aligned with centralaxis 200. In such symmetrical embodiments, the symmetry of cage bar cap40 reduces necessary orientation during manufacturing, such as machiningor extruding cage bar cap 140 and central rib 221. The symmetry alsoreduces part inventory as pre-machined parts may be used on eitherclockwise or counter-clockwise rotating systems.

An advantage common to the embodiments shown in FIGS. 9-10 a is thatthese embodiments can be made easily and inexpensively, such as byextruding profiles corresponding to the cross sectional areas of FIGS.9A and 10A. Extruded profiles can then be cut to length and the ribsmachined to produce the desired contoured surfaces.

In some embodiments, the cage bar itself may include a rib as opposed toseparate cage bars and cage bar caps. For example, FIG. 11 shows anembodiment of a positive drive spiral conveyor system 301 that includesan offset rib 321 having a varying height contour surface 323 that issimilar to offset rib 121 shown in FIG. 9. However, unlike FIG. 9,offset rib 321 extends away from a surface 342 of cage bar 330 insteadof from a cage bar cap. Cage bar 330 is uncapped and attached to drum310. In this embodiment, cage bar 330 and offset rib 321 form a singlemonolithic structure. System 301 otherwise is similar to or the same asany of the systems discussed above.

FIGS. 12 and 12A show another embodiment of a cage bar cap 440configured to provide a contoured surface 423. Like the embodiment ofcage bar cap 140 shown in FIG. 9 in most respects, cage bar cap 440 isconfigured to cover a cage bar (not shown). However, in this embodiment,cage bar cap 440 has some geometrical variations. Cage bar cap 440includes a short offset rib 421. Short offset rib 421 is similar tooffset rib 121, as short offset rib 421 extends away from a surface 442of cage bar cap 440 offset rearward from a central axis 400 a distance452 and a second distance 450 from leading face 430. Short offset rib421 also varies in height along a height of cage bar cap 440.

Unlike offset rib 121, short offset rib 421 is not coextensive with cagebar cap 440. Short offset rib 421 extends from a top 463 of cage bar cap440 to a terminus 424. Terminus 424 is separated from a bottom 464 ofcage bar cap 440 by a distance 410 so that short offset rib 421terminates short of the position at which conveyor belt 415 enters thespiral. This allows cage bar cap 440 to have a smooth bottom portion497. Smooth bottom portion 497 may be beneficial in guiding a conveyorbelt onto contoured surface 423 after allowing the links of the belt tocollapse. Distance 410 may be any distance desired, but may be less than25% of length of cage bar cap 440. Smooth bottom portion 497 may bewider than the rest of cage bar cap 440. In such embodiments, an angledtransition portion 498 connects smooth bottom portion 497 with surface442 to avoid possible jarring lateral motion of the belt as the beltengages short offset rib 421 and also to eliminate a possible nichewhich might be difficult to clean.

Also unlike offset rib 121, short offset rib 421 includes a chamferededge 432. Chamfered edge 432 is positioned on an opposite side of shortoffset rib 421 to a drive face 445. Chamfered edge 432 may be providedto facilitate movement of the belt along short offset rib 421 and/or tofacilitate manufacturing. Chamfered edge 432 extends away from trailingface 433 of cage bar cap 440 at an angle 430. Angle 430 may be any angledesired, but may in some embodiments be between 20 degrees and 90degrees.

FIGS. 13 and 14 show an embodiment of how a cage bar cap 540 on a cagebar 530 may engage with a conveyor belt 515. For clarity, the drum isnot shown, though cage bar 530 would be attached to a drum. Cage bar 530and cage bar cap 540 is similar to any cage bar cap discussed above,though in this embodiment center rib 521 is centrally located on a frontface 532 of cage bar cap 540. Center rib 521 includes a drive face 545configured to engage with a portion of an edge link 527 of a metal belt515.

In FIG. 13, metal belt 515 may include a plurality of generally U-shapedlinks 525 connected by rods 526 in any known manner that permits metalbelt 515 to expand and collapse as it moves through a spiral. In thisembodiment, all links 525 are edge links that form the outermostsurfaces of metal belt 515. In this embodiment, edge links 527 includetabs 514 configured to engage with drive face 545. As shown, drive face545 abuts tab 514 to firmly and yet removably engage metal belt 515while tab 514 may touch or be spaced apart from surface 532. Asdiscussed above with respect to FIG. 9, a thickness of center rib 521may be limited by an interstitial space 555 between adjacent tabs ofadjacent edge links 527, as center rib 521 is designed to fit easilyinto interstitial space 555. In some embodiments, center rib 521 mayextend to edge link 527, while in other embodiments, center rib 521 mayterminate short of edge link 527.

Tab 514 extends away from outer leg 518 of an edge link 527 at a tabangle 516. Tab angle 516 may be any desired angle, but may be between 20degrees and 130 degrees. Tab 514 may include a flat face to provide alarger surface area for the engagement of drive face 545 with tab 514.In such embodiments, tab angle 516 may be about 90 degrees. In thisembodiment, edge links 527 are made from a metal material. As such, tab514 may be formed on outer leg 518 by bending a length of outer leg tothe desired angle. Other methods of manufacturing such an edge featureare also contemplated, such as stamping edge link 527 into the desiredshape.

FIG. 14 shows the embodiment of FIG. 13, but at a different portion ofthe rib where the rib portion 621 is at a greater height above surface532 of cage bar cap 540 on a cage bar 530 of a driving element 520 mayengage with a conveyor belt 515. For clarity, the drum is not shown,though cage bar 530 would be attached to a drum. Cage bar 530 and cagebar cap 540 are similar to any cage bar cap discussed above, though inthis embodiment extended center rib portion 621 is centrally located ona front face 532 of cage bar cap 640. Center rib portion 621 includes adrive face 645 configured to engage with a portion of an edge link 527of a metal belt 515.

Extended center rib portion 621 has a rib height 650 that is higher thana rib height of center rib 521 and the length of tab 514. This greaterheight allows for greater clearance between tab 514 and front face 532for those embodiments where contact between tab 514 and front face 532is not desired, such as when, for example, tab 514 may have a sharp edgethat would increase wear of front 532 and potentially limit a lifespanof cage bar cap 540.

In some embodiments, such as the embodiment shown in FIGS. 15 and 16, asupport structure 773 is provided adjacent to a guide rib 721. In thisembodiment, a cage bar 730 and a cage bar cap 740 of a drive element 720are the same as or similar to any cage bar or cage bar cap discussedabove, particularly those with centrally positioned ribs such as cagebar cap 540. In this embodiment, a tabbed belt 715 is similar to metalbelt 615 as discussed above, with edge links 727 having drive tabs 714.

Support structure 773 is sized and positioned so that when a drive face745 is engaged with a first surface of drive tab 714 of an edge link727, support structure 773 contacts a second surface of drive tab 714 atan engagement point 742 on support structure 773. In the embodimentshown in FIGS. 15 and 16, the first surface is substantiallyperpendicular to the second surface of drive tab 714. This engagementmay lend additional stability to tabbed belt 715 as tabbed belt 715travels through the spiral.

As shown in FIG. 16, support structure 773 may follow the geometry ofguide rib 721 though support structure 773 does not extend as far abovecage bar surface 732 as does guide rib 721. This configuration is sothat engagement tab 714 may be nestled within the L-shape formed byguide rib 721 and support structure 773. For example, in thoseembodiments where guide rib 721 includes a tapered portion 747, supportstructure 773 also includes a taper.

As shown in FIG. 17, ribbed guide structures are not limited toembodiments with metal belts. FIG. 17 shows a plastic link belt 815 thatis formed from a plurality of plastic links 825 joined by elongated rods826. Elongated rods 826 may be made from metal or plastic. In thisembodiment, a cage bar 830 and a cage bar cap 840 of a drive element 820are the same as or similar to any cage bar or cage bar cap discussedabove, particularly those cage bar caps with centrally positioned ribssuch as cage bar cap 540.

In this embodiment, each pitch includes an edge link 827 from which atab 814 protrudes towards an engagement rib 821. Tab 814 is similar toprotrusion 14 as discussed above. Tab 814 may engage with engagement rib821 in any manner discussed above. As shown in FIG. 17, multiple driveelements 820 may be engaged with different corresponding edge links 827simultaneously.

FIG. 18 shows how a chamfered rib 1021 may engage with a metal belt1015. For clarity, the drum is not shown, though cage bar 1030 would beattached to a drum. Cage bar 1030 and cage bar cap 1040 are similar toany cage bar and cage bar cap, respectively, discussed above. In thisembodiment chamfered rib 1021 is centrally located on a front face 1032of cage bar cap 1040. Chamfered rib 1021 includes a drive face 1045configured to engage with a portion of an edge link 1027 of a metal belt1015.

In this embodiment, metal belt 1015 may include a plurality of generallyU-shaped links 1025 connected by rods 1026 in any known manner thatpermits metal belt 1015 to expand and collapse as it moves through aspiral. In this embodiment, all links 1025 are edge links 1027 that formthe outermost surfaces of metal belt 1015. In this embodiment, edgelinks 1027 include tabs 1014 configured to extend away from an edge link1027 and engage with drive face 1045. As shown, drive face 1045 abutstab 1014 to firmly and yet removably engage metal belt 1015.

Tab 1014 may include a flat face to provide a larger surface area forthe engagement of drive face 1045 with tab 1014. In this embodiment,edge links 1027 are made from a metal material. As such, tab 1014 may beformed by bending a length of an outer leg of edge link 1027 to adesired angle. Other methods of manufacturing such an edge feature arealso contemplated, such as stamping edge link 1027 into the desiredshape.

Because chamfered rib 1021 has a chamfered surface 1075, chamfered rib1021 essentially terminates at a point 1044. Point 1044 is thin enoughto slide past tab 1014 and into a niche 1029 between tab 1014 and anadjacent edge link 1027A when tab 1014 is engaged with drive face 1045.Such an engagement may be more stable and secure than ribs that lack achamfered edge or other point-like terminal ends. Chamfered surface 1075may be angled to correspond to an angled portion 1090 of edge link 1027.Chamfered surface 1075 may permit separation of edge links 1027 and1027A such that point 1044 may contact link surface 1091. As will berecognized by those in the art, any chamfered surface of any embodimentdisclosed herein or adapted to have a chamfered surface may also serveas the contoured surface or a portion of the contoured surface.

In some embodiments, conveyor belts may include edge features other thanedge features for engaging with a positive drive system. For example, asshown in FIG. 19, a buttonless belt 1115 may include welds 1192 thatcover the ends of elongated rods 1126. While welds 1192 may be smooth,welds 1192 may protrude away from an outer leg 1118 of an edge link1127. Edge link 1127 may also include an engagement tab 1114 similar toprotrusion 14 or any other tab described above, particularly tab 114, anangled portion of an outer leg of an edge link.

A chamfered rib 1121 of cage bar cap 1140 may engage with buttonlessbelt 1115. Cage bar 1130 and cage bar cap 1140 is similar to any cagebar cap discussed above. In this embodiment chamfered rib 1121 issimilar to chamfered rib 1021 discussed above and is centrally locatedon cage bar cap 1140. In some embodiments, rib 1121 may be sized anddimensioned so that rib 1121 has a clearance gap 1195 between chamferededge 1183 and welds 1192 as rib 1121 moves towards an engagementposition with an engagement tab 1114. This arrangement may prevent orinhibit unwanted motion that would otherwise occur if rib 1121 were tocome into contact with weld 1192. This arrangement may also preventengagement with weld 1192, which may undesirably wear either or both ofrib 1121 and weld 1192.

FIG. 20 shows a similar clearance when a chamfered rib 1283 engages witha buttonhead belt 1215. Buttonhead belt 1215 may include buttonheads1293 that cover the ends of elongated rods 1226. While buttonheads 1293may be smooth, buttonheads 1293 may protrude away from an outer leg 1218of an edge link 1227. Edge link 1227 may also include an engagement tab1214 similar to protrusion 14 or any other tab described above,particularly tab 124, an angled portion of an outer leg of an edge link.

A chamfered rib 1221 of cage bar cap 1240 may engage with buttonheadbelt 1215. Cage bar 1230 and cage bar cap 1240 is similar to any cagebar cap discussed above. In this embodiment chamfered rib 1221 issimilar to chamfered rib 1021 discussed above and is centrally locatedon cage bar cap 1240. In some embodiments, chamfered rib 1221 may besized and dimensioned so that rib 1221 has a clearance gap 1295 betweenchamfered edge 1283 and buttonheads 1293 as chamfered rib 1221 movestowards an engagement position with an engagement tab 1214. Thisarrangement may prevent or inhibit unwanted motion that would otherwiseoccur if chamfered rib 1221 were to come into contact with buttonhead1293. This arrangement may also prevent engagement with buttonhead 1293,which may undesirably wear either or both of chamfered rib 1221 andbuttonhead 1293.

FIG. 21 shows an embodiment of how drive elements 1320 including a cagebar 1330 and a cage bar cap 1340 on a cage bar 1330 may engage with aconveyor belt 1315. Cage bar 1330 is attached to a drum 1310. Drum 1310,cage bar 1330, and cage bar cap 1340 are similar to any drum, cage bar,and cage bar cap, respectively, discussed above, though in thisembodiment rib 1321 is centrally located on a front face of cage bar cap1340. Chamfered center rib 1321 includes a drive face 1345 configured toengage with a portion of an edge link 1327 of a metal belt 1315.

In this embodiment, metal belt 1315 may include a plurality of generallyU-shaped links 1325 connected by rods 1326 in any known manner thatpermits metal belt 1315 to expand and collapse as it moves through aspiral. In this embodiment, edge links 1327 include tabs 1314 configuredto engage with drive face 1345. As shown, rib 1321 abuts tabs 1314 tofirmly and yet removably engage metal belt 1315. Tabs 1314 extend awayfrom outer leg 1318 of an edge link 1327 and are similar to tabs 514discussed above with respect to FIG. 13.

FIG. 21 shows how a top tier 1390 of a spiral may exit the spiral andhead to a return path, such as return path 104 as shown in FIG. 1. InFIG. 21, first drive element 1320 is engaged with a tab 1314, whilesecond drive element 1320A is disengaging from tab 1314A. At the pointof disengagement, links 1325 expand from a first collapsed pitch P1 to asecond expanded pitch P2, resulting in forward movement of links 1325with respect to ribs 1321 and 1321A. The sharp angle of chamfered edge1383A results in no rib material blocking or inhibiting movement of tab1314B. In some embodiments, tab 1314B may even slide along chamferededge 1383 for a smooth, not sudden, movement of tab 1314B past rib1321A. Sudden catching and disengagement of the tabs from the driveelements may damage the drive elements and place unintended forces onthe belt which may reduce the useful life of the belt. In some extremecases, a sudden disengagement may derail the conveyor belt and/or jarconveyed product in undesirable ways.

Similarly, a jarring engagement with the drum at a spiral entrance mayproduce undesirable results. FIGS. 22-24 show how a smooth bottomportion 1497 can help to ease belt 1415 onto a rib 1421. A drum 1410,which is similar to any drum discussed above, includes multiple driveelements 1420 with contoured surfaces 1423. Rib 1421 is a protrusionthat extends away from a base surface of drive element 1420 towards belt1415. Similar to contoured surface 23 discussed above with respect toFIG. 6, contour surface 1423 includes a flat lower section 1448 at afirst height above the base surface of drive element 1420, an uppersection 1446 at a second, lower height above the base surface of driveelement 1420, and a tapered section 1447 that continuously joins lowersection 1448 to upper section 1446.

In this embodiment, drive element 1420 may have a smooth bottom portion1497 that is similar to smooth bottom portion 497 discussed above.Smooth bottom portion 1497 may be beneficial in guiding a conveyor beltonto contoured surface 1423 after allowing the links to collapse. Insome embodiments, smooth bottom portion 1497 may be wider than the restof drive element 1420. In such embodiments, an angled transition portion1487 connects smooth bottom portion 1497 with an outermost surface oflower section 1448 to avoid possible jarring motion of the belt as thebelt connects with rib 1421, as belt 1415 has an opportunity to firsttransition from being frictionally driven by drive element 1420 beforebeginning the trip up the spiral on rib 1421 from spiral bottom 1464 tospiral top 1463. In this embodiment, that transition is further easedbecause bottom portion 1497 has a greater diameter than lower section1448, where the additional tension in a more expanded belt being held ata greater diameter can release onto the lower diameter rib 1421 as belt1415 moves from a first position T1 to a second position T2. In FIG. 24,bottom portion 1497 has essentially the same or a slightly smallerdiameter than flat lower section 1448 of rib 1421. Due to theoverlapping engagement of the link tabs with lower section 1448, belt1415 at T2 may have the same or slightly smaller diameter than belt 1415at T1. A chamber at the bottom of section 1448 provides a smoothtransition from bottom portion 1497 to flat lower section 1448. In suchembodiments, lateral movement is minimized as links 1425 engage ribs1421.

In another embodiment, shown in FIG. 25, instead of a flat bottomportion of a drive element providing the larger diameter, smooth surfacefor onboarding to a rib, drum 1510 includes a lower ring 1598 that isapproximately the same diameter as a lower portion 1548 of a rib 1521.Rib 1521 is associated with a drive element 1520 of drum 1510. Rib 1521includes a flat lower section 1548 at a first height above the basesurface of drive element 1520, an upper section 1546 at a second, lowerheight above the base surface of drive element 1520, and a taperedsection 1547 that continuously joins lower section 1548 to upper section1546. Drum 1510, drive element 1520, and rib 1521 may have the samefeatures as any drum, drive element, or rib, respectively, discussedabove. Ring 1598 performs the same or a similar function as bottomportion 1497 discussed above by allowing belt 1515 to collapse on smoothring 1598, then drum 1510 advances belt 1515 on to positively engage rib1521.

FIG. 26 shows an embodiment of a drum 2010 that includes a similarribless portion 2041 of a drive element 2020 proximate a top 2063 ofsystem 2001. In this embodiment, drum 2010, drive element 2020, cage barcap 2040, and rib 2021 may be similar or the same as any drum, driveelement, cage bar cap, and rib discussed above. Similar to rib 1521, rib2021 includes a flat lower section 2048 at a first height above the basesurface of cage bar cap 2040, an upper section 2046 at a second, lowerheight above the base surface of cage bar cap 2040, and a taperedsection 2047 that continuously joins lower section 2048 to upper section2046.

Proximate bottom 2064, drive bar cap 2040 includes a smooth bottomportion 2097 that is similar in form and function to smooth bottomportion 1497 as discussed above. Ribless portion 2041 performs a similarfunction proximate top 2063. In embodiments where rib 2021 terminates atan upper point 2095 on cage bar cap 2040. Upper point 2095 is separatedfrom a cage bar top 2042 of cage bar cap 2040 so that rib 2021terminates short of the position at which conveyor belt 2015 exits thespiral. Ribless portion 2041 allows for belt 2015 to expand unhindered.This may allow for more tension control of belt 2015 as belt 2015 exitsthe spiral and is pulled by a take up reel such as take up roller 115shown in FIG. 1, which may inhibit slippage of belt 2015.

While various embodiments have been described, the description isintended to be exemplary, rather than limiting, and it will be apparentto those of ordinary skill in the art that many more embodiments andimplementations are possible that are within the scope of theembodiments. Any feature of any embodiment may be used in combinationwith or as a substitute for any other feature or element in any otherembodiment unless specifically restricted. Accordingly, the embodimentsare not to be restricted except in light of the attached claims andtheir equivalents. Also, various modifications and changes may be madewithin the scope of the attached claims.

The invention claimed is:
 1. A spiral conveyor system comprising: a drumassociated with a motor, wherein the drum extends from a drum bottom toa drum top; a conveyor belt traveling helically about the drum from anentrance end of the drum to an exit end of the drum; a rib associatedwith the drum, wherein the rib extends radially from a surface of thedrum; wherein the rib includes at least one drive face; wherein theconveyor belt includes at least one belt surface configured to engagethe at least one drive face; wherein the length of the rib extends alongthe length of the drum from a first end of the rib to a terminus of therib proximate the entrance end of the drum; wherein the drum includes aring that extends between the terminus of the rib and the entrance endof the drum; wherein the surface of the drum defines a first diameter ofthe drum; and wherein the ring has a diameter that is larger than thefirst diameter of the drum.
 2. The spiral conveyor system of claim 1,wherein the rib defines a second diameter of the drum; and wherein thering has a diameter that is approximately the same as the seconddiameter of the drum defined by the rib at the terminus of the rib. 3.The spiral conveyor system of claim 1, wherein the rib defines a seconddiameter of the drum; and wherein the ring has a greater diameter thanthe second diameter of the drum defined by the rib at the terminus ofthe rib.
 4. The spiral conveyor system of claim 1, wherein the rib has afirst height at the terminus; wherein the first height is the maximumheight of the rib along the length of the rib; and wherein at least aportion of the rib has a tapered height.
 5. The spiral conveyor systemof claim 1, wherein the first end of the rib is spaced from the exit endof the drum such that the drum includes a ribless portion at the exitend of the drum.
 6. The spiral conveyor system of claim 1, wherein thedrum includes a plurality of drive elements defined by a plurality ofcage bars.
 7. The spiral conveyor system of claim 6, wherein the systemincludes a plurality of cage bar caps configured to cover the cage bars.8. The spiral conveyor system of claim 7, wherein an entrance end of atleast one cage bar cap of the plurality of cage bar caps is spaced fromthe entrance end of the drum such that the ring is provided between theentrance end of the drum and the entrance end of the at least one cagebar cap.
 9. The spiral conveyor system of claim 6, wherein the systemincludes a cage bar cap including the rib; and wherein the ring of thedrum is a separate component attached to, and overlapping a portion of,the cage bar cap.
 10. The spiral conveyor system of claim 6, wherein atleast a part of the ribless portion extends between two or more of thedrive elements.
 11. The spiral conveyor system of claim 1, wherein thering comprises more than 50% of the circumference of the drum.
 12. Thespiral conveyor system of claim 11, wherein the ring is substantiallycontinuous.
 13. The spiral conveyor system of claim 1, wherein the ringis a separate component from the cage bar cap.
 14. The spiral conveyorsystem of claim 1, wherein the ring is a replaceable wear component. 15.The spiral conveyor system of claim 14, wherein the ring is made ofplastic.
 16. The spiral conveyor system of claim 1, wherein the ringabuts a terminus of the rib.
 17. A spiral conveyor system comprising: adrum associated with a motor, wherein the drum extends from a drumbottom to a drum top; a conveyor belt traveling helically about the drumfrom an entrance end of the drum to an exit end of the drum; a ribassociated with the drum, wherein the rib extends radially from asurface of the drum; the rib having at least one drive face configuredto engage at least one belt surface; wherein the drum includes a ringthat extends around the drum proximate the entrance end of the drum, thering having a substantially smooth surface extending circumferentiallyaround the drum; wherein the surface of the drum defines a firstdiameter of the drum; and wherein the ring has a diameter that is largerthan the first diameter of the drum.
 18. The spiral conveyor system ofclaim 17, wherein the rib defines a second diameter of the drum; andwherein the ring has a diameter that is approximately the same as thesecond diameter of the drum defined by the rib at a terminus of the ribproximate the entrance end of the drum.
 19. The spiral conveyor systemof claim 17, wherein the rib defines a second diameter of the drum; andwherein the ring has a greater diameter than the second diameter of thedrum defined by the rib at a terminus of the rib proximate the entranceend of the drum.
 20. The spiral conveyor system of claim 17, furtherincluding a plurality of drive elements defined by a plurality of cagebars; wherein the system includes a plurality of cage bar capsconfigured to cover the cage bars; and wherein the ring is a separatecomponent from the cage bar caps.